During the fabrication process of integrated circuits (IC), defective components may be produced along the production chain. Defective components may increase costs by creating additional production time and limiting production throughput. Therefore, it is important to test for such defective components to prevent such added costs of defective components. For example, an IC such as a transceiver component may be included in wireless communication devices. The transceiver component may be individually tested before it further passes along the production chain. To this end, a fast and efficient testing process of the transceiver component may have a significant effect in production costs.
A loop back test to test radio frequency (RF) functionality of the transceiver component may use external RF signal generators and external mixers (i.e., generators and mixers that are not part of the transceiver). A particular test is the loop back test to test RF functionality, where the transceiver component feeds the transmit output signal (i.e., RF frequency signal) back into the receiver component for test purposes. The external RF signal generators and mixers used to implement testing of the transmit part and the receive part in the transceiver component may require additional time and cost in the production process.
In certain implementations, the loop back test to test the RF functionality of the transceiver component may avoid the use of the external RF signal generators and mixers implemented in the transceiver component; however, the loop back test implementation may contain additional components such as a frequency shift circuit and an attenuator that are integrated into the transceiver component. During the test mode operation, the frequency shift circuit may adjust the frequency of the loop back transmit output signal into a predefined frequency of a receiver input signal to be received by the receiver. The frequency shifted transmit output signal may further undergo attenuation in the attenuator. The attenuator may adjust the amplitude of the frequency shifted transmitter output signal to substantially match a predefined amplitude of a receiver input signal received by the receiver. The predefined frequency and predefined amplitude of a receiver input signal may refer to the frequency and amplitude of the signal used as reference signals for the loop back test. A pass or fail status may be determined by comparing the measured output at a test point in the receiver output, with that of the predefined frequency and predefined amplitude as reference signals for test purposes.
A loop back test with the additional circuitry such as a frequency shift circuit and an attenuator can have disadvantages. One disadvantage may be additional area requirement, and another disadvantage may be a degradation of the circuit properties in normal operation mode. The additional area requirement may result due to the additional frequency shift circuit and attenuator implemented in the transceiver chip. The degradation of the circuit properties in the normal operation mode may result due to attenuations produced by switches added by the frequency shift circuit and attenuator.
A transceiver component may also use a single phase locked loop (PLL) to support both transmit and receive components; however, with a PLL, the disadvantages of additional area requirements may be further emphasized. In order to correct the additional area requirements, a loop back self test using the functional circuit components may be performed by applying an amplitude modulation in the receiver component. The amplitude modulation, which may include low frequency modulation, may be applied in the receiver component to modulate the received RF signal from the loop back transmit output. A measurement at a test point in the receiver component output may include signal strength measurement (due to amplitude modulation), to determine the pass or fail status of the transceiver component.